From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH v4 3/4] leds: core: add documentation for color extension Date: Wed, 02 Mar 2016 09:25:03 +0100 Message-ID: <56D6A35F.4020809@samsung.com> References: <56CF7C85.7030005@gmail.com> <56D46E58.5070508@samsung.com> <56D4A91C.30309@gmail.com> <56D56025.4080201@samsung.com> <56D6011D.8090501@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mailout2.w1.samsung.com ([210.118.77.12]:11124 "EHLO mailout2.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753549AbcCBIZH (ORCPT ); Wed, 2 Mar 2016 03:25:07 -0500 Received: from eucpsbgm1.samsung.com (unknown [203.254.199.244]) by mailout2.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0O3E00CZQKPSP810@mailout2.w1.samsung.com> for linux-leds@vger.kernel.org; Wed, 02 Mar 2016 08:25:04 +0000 (GMT) In-reply-to: <56D6011D.8090501@gmail.com> Sender: linux-leds-owner@vger.kernel.org List-Id: linux-leds@vger.kernel.org To: Heiner Kallweit Cc: linux-leds@vger.kernel.org On 03/01/2016 09:52 PM, Heiner Kallweit wrote: > Am 01.03.2016 um 10:25 schrieb Jacek Anaszewski: >> On 02/29/2016 09:25 PM, Heiner Kallweit wrote: >>> Am 29.02.2016 um 17:14 schrieb Jacek Anaszewski: >>>> On 02/25/2016 11:13 PM, Heiner Kallweit wrote: >>>>> Document the color extension in Documentation/leds/leds-class.txt >>>>> >>>>> Signed-off-by: Heiner Kallweit >>>>> --- >>>>> v2: >>>>> - introduced to patch series >>>>> v3: >>>>> - document extension in more detail >>>>> v4: >>>>> - Better explain why flag LED_SET_HUE_SAT is needed >>>>> --- >>>>> Documentation/leds/leds-class.txt | 27 ++++++++++++++++++++++----- >>>>> 1 file changed, 22 insertions(+), 5 deletions(-) >>>>> >>>>> diff --git a/Documentation/leds/leds-class.txt b/Documentation/leds/leds-class.txt >>>>> index d406d98..b1e4cba 100644 >>>>> --- a/Documentation/leds/leds-class.txt >>>>> +++ b/Documentation/leds/leds-class.txt >>>>> @@ -8,6 +8,22 @@ LED is defined in max_brightness file. The brightness file will set the brightne >>>>> of the LED (taking a value 0-max_brightness). Most LEDs don't have hardware >>>>> brightness support so will just be turned on for non-zero brightness settings. >>>>> >>>>> +If a driver uses the colour extension of the LED core then the brightness >>>>> +file can be used to set hue / saturation / value. The brightness value is >>>>> +interpreted as: <0000000F> >>>>> +Usage of the least byte is identical to monochrome mode. Saturation can be >>>>> +0-255 and hue 0-251 (Colour circle is mapped to 0-252). >>>>> +If hue and saturation both are 0 the current colour is preserved and only >>>>> +the brightness is set. This ensures backwards compatibility with monochrome >>>>> +mode, e.g. for led_set_brightness() calls from triggers. >>>>> +However we might want to have the option to set all HSV components, even >>>>> +if hue and saturation both are 0 (e.g. via brightness sysfs attribute). >>>>> +Use case: Set color to white (hue = 0 and saturation = 0). >>>>> +Therefore the default behaviour can be overridden with flag F (LED_SET_HUE_SAT). >>>>> +If this flag is set then hue and saturation are not checked for being 0 and >>>>> +the color components are set unconditionally. Example: >>>>> +0x010000ff sets the LED to white color with full brightness. >>>> >>>> I was thinking especially about highlighting the use case when we set >>>> different hue and sat for different LEDs that are registered on some >>>> trigger, and a driver that is currently unaware of LED RGB extension can >>>> set only brightness and the LEDs will react with changing their >>>> colors but each of them in different manner, according to the hue >>>> and sat set. >>>> >>> I have to admit that I have a hard time trying to understand what you mean. >> >> I was writing this in a hurry - sorry about that. >> >>> With >>> "a driver that is currently unaware of LED RGB extension can set only brightness" >>> you mean a driver calling led_trigger_event? >>> Arguments to led_trigger_event are always <= LED_FULL what means that the (potential) >>> color of all LEDs attached to the trigger isn't touched. >> >> Changing brightness in HSV model influences resultant color, doesn't it? >> > Not in general, see led_rgb_adjust_hue_sat(). > If brightness <= LED_FULL then hue and sat aren't touched. Only the value > component is changed. Right, but change in value entails change in all three R G B components, which together compose resultant color. >>>>> The class also introduces the optional concept of an LED trigger. A trigger >>>>> is a kernel based source of led events. Triggers can either be simple or >>>>> complex. A simple trigger isn't configurable and is designed to slot into >>>>> @@ -45,11 +61,12 @@ Is currently of the form: >>>>> >>>>> "devicename:colour:function" >>>>> >>>>> -There have been calls for LED properties such as colour to be exported as >>>>> -individual led class attributes. As a solution which doesn't incur as much >>>>> -overhead, I suggest these become part of the device name. The naming scheme >>>>> -above leaves scope for further attributes should they be needed. If sections >>>>> -of the name don't apply, just leave that section blank. >>>>> +If the colour extension is used hsv / rgb can be used instead of a specific >>>>> +colour. There have been calls for LED properties such as colour to be >>>>> +exported as individual led class attributes. As a solution which doesn't >>>>> +incur as much overhead, I suggest these become part of the device name. >>>>> +The naming scheme above leaves scope for further attributes should they be >>>>> +needed. If sections of the name don't apply, just leave that section blank. >>>>> >>>>> >>>>> Brightness setting API >>>>> >>>> >>>> >>> >>> >>> >> >> > > > -- Best regards, Jacek Anaszewski